This invention relates to a method and apparatus for inserting wire pins into substrate holes to form wire wrap connectors for circuit boards, pins of electrical connectors, or the like. The method and apparatus of the present invention are particularly applicable for straightening, feeding, and preforming a continuous length of solid wire to provide a string of interconnected square or round wire wrap pins and for sequentially handling, separating, inserting, and driving a front pin of the string into preformed holes of a printed circuit board in an automatic, in-line, process. Additional preforming of the continuous wire or interconnected, preformed string of wire pins is contemplated to provide a flute-type of deformation of the individual pins in order to provide an interference fit of the pins with the circuit board.
Prior art devices have utilized reels of preformed, interconnected wire pins for insertion into printed circuit board holes. Further, one prior device of which applicants are aware provides for straightening and feeding a continuous length of solid wire to a preform station, preforming the continuous length into interconnected, preformed pins, and inserting the pins individually into selected holes of a printed circuit board. These prior art devices have proven generally to be efficient at handling wire pins, for instance, having a square cross-section with each side of the square having a dimension on the order of 0.045 inches. However, in attempting to handle and properly insert wire pins of smaller cross-sectional dimensions, for instance, the side of a square cross-section on the order of 0.025 inches, great difficulty has been encountered. The greatest difficulties in such an adaptation of prior art devices to handling of pins of such small dimensions has been in the loss of control of the pins and breakage of the means for driving the pins into the holes of the circuit boards. It has been found that, in trying to scale-down the component parts of prior art devices to a size which will handle such small dimension pins, that the parts for handling these pins become so small in cross-section and filmsy that they cannot bear the pressures inherent in such apparatus without breaking at fairly regular intervals of use. It has also been found, in the in-line continuous feeding, forming, and inserting apparatus of the prior art, that loss of control of an individual pin often occurs upon separation thereof from the string of preformed pins during reorientation of a separated pin for insertion into the circuit board hole.
Accordingly, among other objects which will become apparent from the following description, it is an object of the instant invention to handle square or round cross-section wire pins of smaller dimensions than heretofore possible in a consistent, continuous, and automatic manner of feeding, forming, and inserting of the pins into selected holes of a circuit board, without loss of control of the pin once it has been disconnected from a string of preformed pins and while providing an apparatus which consistently inserts the separated pin into the circuit board without the well-known "down times" associated with breakage of insert tooling that occurs when handling pins of such small dimensional cross-sections.
In obtaining the objects of the instant invention, wire stock is fed from a reel supply through an in-line series of wire-straightening rollers, an incremental feeder, and swaging tools for preforming the wire into a string of interconnected preformed pins. The string of preformed pins is fed at an angle to the plane of a printed circuit board into an insertion head which separates an individual pin from the string, while controlling the individual pin during a reorientation thereof for insertion into a circuit board hole and driving the reoriented pin into the hole. The particular means for controlling pins of such small cross-sectional dimensions will be better understood from the following description.